Re: [PATCH 3/3] xen/public: arch-arm: All PSR_* defines should be unsigned

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 18/08/2023 09:14, Jan Beulich wrote:
> On 18.08.2023 09:39, Julien Grall wrote:
> > On 18/08/2023 07:33, Jan Beulich wrote:
> > > As an aside I wonder why they're here: They look like definitions of
> > > processor registers, which aren't under our (Xen's) control.
> > I agree they are not under Xen's control. However, they are used by the
> > toolstack and IIRC back then they were not available in any other headers.
> >
> > Note that they are only available by the tools and the hypervisor (see
> > #ifdef above).
> Yes, I did notice that (or else I would have used stronger wording).
>
> > > I ask in
> > > part because the presence of such constants may then be taken as
> > > justification to add similar things in new ports. Yet such definitions
> > > shouldn't be put here.
> >   From my understanding we are using the public headers to provide
> > macros/defines that are used by both the toolstack and the hypervisor.
> > If they are not meant to be exposed to the guest, then they will be
> > protected with "#if defined(__XEN__) || defined(__XEN_TOOLS__)".
> >
> > I think we are in a similar situation here. So it is not clear where
> > they should be put if we need to share them between the hypervisor and
> > the toolstack.
> On x86 we simply arrange for certain hypervisor headers to be re-usable
> from the toolstack. See in particular arch/x86/include/asm/x86-*.h. And
> of course everything under include/xen/lib/x86/, but those are our own
> definitions, not ones meant to solely express relevant hw spec aspects.
Even if they are defined by the HW, we still need them to easily create 
some hypercalls field.
If we are planning to have a stable toolstack ABI (as Juergen 
suggested), then I would find a bit odd that onewould need to include 
lib/ (or provide their own header) in order to update the fields.
Anyway, I am not planning to do any re-ordering anytime soon for the 
public. But I would be happy to take part of the discussion if there are 
a general agreement to split further and someone wants to write patches.
Cheers,

--
Julien Grall